I've never seen it listed as 'Missing' before, since it's Microsoft's own algorithm that's responsible for determining it. Perhaps an earlier phase has already rejected all of the recipients at the SMTP stage, leaving a directionless message that gets flagged for deletion. I don't think the sender domain whitelist applies at this point, though. If you can, try to catch a few messages from the sender as they come in and look at the SMTP conversations. Perhaps their MTA is mangling a standard header in a way that's causing this (unlikely, but it's where I'd look next).

Looks like you are barking up the right tree. The email is an automated report from a program and it looks like the FROM is set to the program name rather than a valid email address. So now, it is just a matter of getting the vendor to configure their software correctly. Thanks for your help.
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sgmooreNov 30 '10 at 10:10

+1 to that. Also bear in mind that the command in the original question will overwrite the array of domains set using this method, so be careful with your powershell...
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SmallClangerNov 25 '10 at 20:22

I am aware of that issue and always check the before and after results whenever I change anything. In this case there were no pre-existing entries and the setting is definitely correct.
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sgmooreNov 26 '10 at 9:19